Java basics at dallas technologies

JAVA Basics Dallas Technologies

About UsDallas Technologies, an ISO 9001:2008 certified company, based at Bangalore India, Providing services in software consulting, application development, outsourcing services, Recruitment and Training. Started operation in the year 2001. We design, build, and support customized applications for businesses large and small. We are the market leader in training and outsourcing in various technologies. We ,Dallas technologies, serve and support IT companies in the areas of Mainframes, ERP, .net, Java/J2EE,Data Warehousing and Business Intelligence, etc. we also train and outsource fresh talents to our clients.

What is java?• A general-purpose object-oriented language.

• Write Once Run Anywhere (WORA).

• Designed for easy Web/Internet applications.

• Widespread acceptance.

History• James Gosling - Sun Microsystems• Co founder – Vinod Khosla

• Oak - Java, May 20, 1995, Sun World

• JDK Evolutions• JDK 1.0 (January 23, 1996)

• JDK 1.1 (February 19, 1997)

• J2SE 1.2 (December 8, 1998)

• J2SE 1.3 (May 8, 2000)

• J2SE 1.4 (February 6, 2002)

• J2SE 5.0 (September 30, 2004)

• Java SE 6 (December 11, 2006)

• Java SE 7 (July 28, 2011)

Why Java is Important

• Two reasons :

• Trouble with C/C++ language is that they are not portable and are not platform independent languages.

• Emergence of World Wide Web, which demanded portable programs

• Portability and security necessitated the invention of Java

Cont..

• J2SE(Java 2 Standard Edition) - to develop client-side standalone applications or applets.

• J2ME(Java 2 Micro Edition ) - to develop applications for mobile devices such as cell phones.

• J2EE(Java 2 Enterprise Edition ) - to develop server-side applications such as Java servlets and Java ServerPages.

Cont…

• Java does not support global variables. Every method and variable is declared within a class and forms part of that class.

• Java does not allow default arguments.

• Java does not support inheritance of multiple super classes by a sub class (i.e., multiple inheritance). This is accomplished by using ‘interface’ concept.

• It is not possible to declare unsigned integers in java.

• In java objects are passed by reference only. In C++ objects may be passed by value or reference.

Cont…New features added in Java:

• Multithreading, that allows two or more pieces of the same program to execute concurrently.

• C++ has a set of library functions that use a common header file. But java replaces it with its own set of API classes.

• It adds packages and interfaces.

• Java supports automatic garbage collection.

• break and continue statements have been enhanced in java to accept labels as targets.

• The use of unicode characters ensures portability.

Cont…Features that differ:• Though C++ and java supports Boolean data type, C++ takes any

nonzero value as true and zero as false. True and false in java are predefined literals that are values for a boolean expression.

• Java has replaced the destructor function with a finalize() function.

• C++ supports exception handling that is similar to java's. However, in C++ there is no requirement that a thrown exception be caught.

Characteristics of Java

• Java is architecture-neutral• Java is portable• Java’s performance• Java is multithreaded• Java is dynamic• Java is secure

• Java is simple• Java is object-oriented• Java is distributed• Java is interpreted• Java is robust

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